Ink-jet and bubble-jet printers have become in recent years increasingly popular in the high-volume and low-cost end of the printer market. They produce good quality prints at a relatively low cost compared to, for example, laser printers and as such they are well suited for small business and domestic users. However, there is scope for reducing further the cost and size of such printers.
A conventional ink-jet printer comprises a printer cartridge which is mounted on a carriage for movement to and fro across the width of the paper. The cartridge comprises a supply of ink and means for directing the ink from a plurality of fine nozzle outlets toward the paper. A number of other elements will also be provided either as part of the printer cartridge or the carriage. These include, for example, thermal elements for producing the ink-jets, paper sensing means, and position encoding means for determining the position of the carriage relative to the main body of the printer and the paper.
However, the main printer head control means, which tells the printer cartridge what to print and where depending on an input from an external source such as a personal computer, is located remote from the printer cartridge and is connected to the cartridge by a flexible cable. Depending on the number of print nozzle outlets provided in the cartridge, the flexible cable will require a large number of individual wires, as much as 50 or 60 or even more. Such cables are well known and the individual wires are generally disposed to form a flat wide cable.
These cables are, however, expensive and in the low-end of the printer market they represent a significant amount of the total cost of a printer. Furthermore because they connect to a moving printer head they must be quite long to allow for this movement and a substantial empty space must be left in the printer so as to allow the cable to move without obstruction as the printer head moves to and fro. This increases the size of the printer beyond what would otherwise be necessary and thus further increases the cost of the printer.
Such flexible cables present further difficulties. The individual wires tend to be very fine and can thus easily break, especially when subject to repeated bending as the printing head moves back and forth, and they are also subject to noise interference unless the cable is shielded, and shielding the cable further adds to the cost of a printer.
U.S. Pat. No. 5,567,063 discloses a partial solution to these problems. In U.S. Pat. No. 5,567,063 a cordless printing head control system is described in which the need for a data-transmitting cable is eliminated. In this patent the printer head is provided with a memory buffer of sufficient storage capacity to store at least one line of data for printing, and this memory buffer is provided with fresh data every time the printer head comes to one end of its travel.
Although an advance on the prior art, the arrangement of U.S. Pat. No. 5,567,063 does not solve all the problems. In particular means have to be provided for moving the printer head across the paper and in U.S. Pat. No. 5,567,063 this is done in a conventional manner with the printer head being driven through a timing belt driven in turn from a drive motor. The provision of a timing belt and of the drive motor both occupy space in the printer militating against further reduction in size, and also add to cost. Furthermore a separate power cable must go to the printer head to provide a source of power.